Certain forms of multiple axle self-steering railway trucks are known, particularly for use in railway cars. Several forms of such self-steering car trucks are disclosed in the above identified prior applications. The truck arrangements disclosed in my prior applications comprise a pair of axled wheelsets mounted in a truck frame structure with freedom for relative yaw motion of the axles and each axled wheelset having a steering arm, with the two steering arms interconnected in a region between the axles to provide for interchange of steering forces between the steering arms and thus provide for interchange of steering forces between the wheelsets in the yawing sense.
In said prior applications, arrangements are shown in which the devices which interconnect the steering arms are arranged to interchange the steering forces between the steering arms and the wheelsets independently of yaw-inducing connection with the main frame or other parts of the truck structure. The foregoing provides self-steering action of such effectiveness and accuracy as to virtually eliminate the angle of attact between the wheel flanges and the rails on which the truck is travelling. Smoother tracking is thereby provided under all conditions. This greatly reduces noise and wear between the wheels and rails in curves, improves high speed stability and ride quality with reduced maintenance of the track, trucks and car structure.
One of the principal objectives of the present invention is to provide a self-steering action of the character just referred to in a powered truck of a locomotive and to adapt this self-steering character to the powered truck of a locomotive in such a manner as to provide for effective delivery of the driving force from the driven wheelsets to the main frame of the truck and thus to the locomotive itself, notwithstanding the freedom provided for the self-steering activity of the wheelsets in the yawing sense.
Another objective of the present invention is to provide a novel arrangement of brakes and brake parts for the driven wheels, the brake equipment being mounted at least in part on the main frame of the truck, but being arranged to accommodate yawing motions of the wheelsets even at times during the application of the brakes.
In one preferred embodiment according to the present invention, the powered truck incorporates two wheelsets, each provided with a steering arm and each of which wheelsets is independently motorized, i.e., the axle of each wheelset carries its own driving motor, and abutment means are provided for transmitting motor torque forces directly from the motor to the truck frame. In another embodiment abutment, means are provided for transmitting torque forces through the steering arms to the truck frame.
It is a further object of the present invention to provide a pivotal interconnection structure between the steering arms associated with each axle wheelset, the interconnection structure being arranged to transmit traction forces between the steering arms, provision also being made to transmit traction forces from the steering arms to the truck frame in various different relatively angled positions of the steering arms.
In summary of the foregoing and of other features of the present invention, it will be seen that it is a general objective of this invention to improve the tracking behavior of railway locomotive trucks, particularly a two-axle or two-wheelset truck. Such improvement in the tracking behavior increases the adhesion available for traction and further reduces the flange forces and thus the wear on both the wheels and the track not only in curves but also on straight track.
Prior art or conventional powered trucks exert lateral forces on the track which are generally much greater than those required to guide the vehicle along the track centerline. In curves, most of the extra lateral force is the result of tracking errors for the leading axle which, in conventional trucks, is restrained to remain parallel with the trailing axle, in consequence of which, the leading axle will have a substantial angle of attack with respect to the rail in the yawing sense. This angle of attack not only creates unnecessary lateral force, but also causes a substantial loss of potentially available longitudinal adhesion for pulling the train. In curves, additional dynamic forces result from the fact that the leading axle, having a large angle of attack, will tend to follow, in detail, all the irregularities present in the alignment of the rails.
The foregoing disadvantages are virtually eliminated by the provision of the self-steering arrangement for a powered truck as provided in accordance with the present invention.
In prior art powered trucks operating on straight track, there are unnecessary lateral forces arising from unneeded steering action, which lateral forces can be of sufficient magnitude to cause wheel flange-to-rail impact, and such impacts have commonly occurred at a frequency approximating 2 to 5 impacts per second. These undesirable motions have arisen with conventional powered trucks in which the axles, while remaining generally parallel to each other, can move individually with substantially no restraint within the longitudinal and lateral clearances present in the mounting of the axle-bearing structures in the pedestal jaws of the truck frame.
The self-steering type of powered truck of the present invention eliminates the unnecessary lateral motions and forces above referred to.
The arrangement of the present invention is adapted for use in powered trucks having axle-hung traction motors. This type of powered truck is especially subject to tracking errors induced by the combination of pedestal jaw clearances and the lateral forces acting at the motor nose. The pedestal clearances allow lateral motion of the truck frame relative to the axle. This motion causes an undesirable yaw motion of the motor/axle assembly through the lateral force at the motor nose which is located longitudinally a substantial distance from the axle.
The arrangement of the present invention is effective in providing self-steering even with axle-hung traction motors. The reason for this is that the motor/axle assembly is firmly guided in yaw by the steering arms within the lost motion of the pedestal clearances. Further, in one embodiment, the motor nose is supported directly by the steering arm, completely eliminating all influence of lateral motor nose forces.
Although it is theoretically possible to support the traction motors from the vehicle body or truck frame instead of from the axles, and provide a flexible coupling in the drive train between the motor and the axles, this approach introduces the mechanical complexity of the flexible coupling and this is a substantial structural drawback. On the other hand, the arrangement of the present invention provides the opportunity to support the traction motors from the steering arms. This greatly reduces the motions imposed on the flexible coupling, making this a much more attractive option for removing the traction motor from the unsprung axle weight category.
In summary, it is pointed out that the arrangements of the present invention effectively provide for steering motions of the powered axles which minimize the wheel/rail angle of attack in curves and also provide a stabilizing restraint of undesirable axle activity on straight track.
In accordance with the present invention, the vertical load-carrying connection between the truck framing and the axles has flexibility in the longitudinal direction to allow for yaw motion of the axles relative to the framing. The interconnection between the steering arms is arranged in a region midway between the two axles of a two-axle powered truck; and according to the present invention, this interconnection provides for interchange of lateral, vertical and longitudinal forces between the two axles, without significantly restraining the relative yaw motion as required in order to permit the axles to assume radial positions with respect to curved track. The interconnection also serves to transmit yaw forces from one wheelset to the other. At the same time, in accordance with the present invention, the interconnection between the steering arms provides a relatively stiff restraint of differential steering motion such as would be required for the two axles to assume positions corresponding to the sides of a non-rectangular parallelogram; and this restraint is of importance in order to provide high-speed stability on straight track.
The foregoing factors are of special importance in a powered truck of a locomotive, because preventing the wheel/rail angle of attack associated with tracking errors causes a consequent increase in the overall adhesion and thus in the utilization of the available power of the driving motors.
It is also a major objective of the present invention to provide for the retrofitting of certain existing powered trucks by adding steering arms and other related equipment to provide the operating advantages above referred to.